Maksutov telescopes are another variant on Cassegrain optics. In principle, they work just the same as a Schmidt-Cassegrain telescope. They have a spherical primary mirror and a secondary mirror. This design is the same. The difference to the Schmidt-Cassegrain with the Maksutov is in its meniscus-shaped lens at the front aperture and no Schmidt plate. This lens goes back to the Russian optical engineer Dmitry Dmitriyevich Maksutov. The constant thickness of the lens means that the system only has a small amount of chromatic aberration. It also corrects the spherical aberration produced by the main mirror. The secondary mirror of the system is a metal coating vapour-deposited onto the back of the meniscus lens. So the design dispenses with spider vanes which could degrade the image. Due to the relatively small secondary mirror obstruction can be kept small. The optics provide very good contrast, coming close to that of a refractor.
Although this telescope has many advantages, there are some downsides of course, as no optical design is perfect in every respect. It also has a long cool-down time. This telescope design has a relatively high weight due to the lens. Similarly to the Schmidt-Cassegrain, the Maksutov has a small field of view with its aperture ratio of between 1:10 and 1:13. Fast optical systems are not possible with Gregorian systems (employing a hole in the primary mirror), as existing aberrations are amplified.